Copper chromium ferrous alloys



Patented July 10, 1928.

UNITED STATES- PATENT OFFICE.

COPPER CHROMIUM FERROUS ALLOYS.

No Drawing. Application filed April 7,

This application is a continuation in part of my copending application Serial 584,552, filed August 26, 1922. The claims in said prior application are directed -to the proportions of copper and chromium without reference to the silicon, whereas theelaim's ot' the present application are directed particularly to the inclusion of the silicon in a copper-containing copper-chrome ferrous alloy.

The present invention relates to copper chromium ferrous alloys, and particularly to alloys containing a sufficient percentageof chromium and copper as to render them substantially non-corrodible and acid resistant.

The invention relates more especially to alloys containing over 2 or 3% chromium, and particularly to so-called stainless steels which usually contain from 8 to 25% of chromium. I have found that if the proper amount of copper be added to such chrome steels, the stainless qualities are not only enhanced, but the steel is made substantially resistant to acids. The copper also tends to make the steel more malleable and easier to work. I have also found that the'malleability and resistance to corrosion may be increased, particularly with high carbon steels, by the presence of silicon with the copper.

The so-called stainless steels usually contain between 8 and 25% of chromium together with hardening carbon usually 1% or over. These steels are stainless or rustless only when hardened and polished, and they are not resistant to strong acids. I have found that by the addition of from .15 to 5% of copper, such steels are made more rust and stain resisting and also acid resistant. The acid resistant properties begin to appear with the addition of about 15% of copper, but are not so markedly present until about .5% of copper is added. I prefer to use about 2 to 3% of copper. Such percentage of copper renders .the steels resistant to stain and rust, not only when hardened and polished, but also when in the annealed and roughened state. The steels are also extra-. ordinarily resistant to strong acids, such as hydrochloric and sulphuric. They are resistant to corrosion in those industrial atmospheres where the air is contaminated with sulphurous and combustion gases. The.

copper also" increases the flame resisting properties of such steels by increasing their 1924. Serial No. 704,633.

resistance to oxidation at high temperaturt-n \Vhile the stain, rust and acid resisting qualities of my copper chromium steel are e: pecially pronoimced in the so-called stainless steel range of chromium, namely 8'7 or over, they show extraordinarily good resistance to corrosion and acid attack when containing lower percentages of chromium, say down to 2 or 3%, although it is not so strongly resistant as with the higher percentages of chromium. I

The copper, in addition to rendering the alloy more resistant to corrosion and acids, increases its'malleability, ductility and dy namic strength.

The susceptibility to corrosion and acid attack increases with the amount of carbon content so that to obtain the same corrosion and acid resisting qualities,'the amount of chromimn and copper should be increased for the higher carbon contents. The higher carbon content, of course, also tends to make the alloy harder and more difficult to fabr1cate. The effect of the higher carbons may be counteracted to a considerable extent by the addition of silicon to thealloy in percentages varying from .5 to 6%, prefer ably about 1 to 3%. counteracts the effect of the carbon and tends tomake the alloy non-corrosive and more malleable so that it may be; more readily rolled and fabricated.

In forming the, alloy, sufficient carbon should be present to give the desired tensile strength and hardness desired. The carbon will in general range from .1 up as high as in the neighborhood of 2% for special steels. The chromium and copper apparently react with the carbon and tend toinaintain it as hardening carbon and prevent its segregation as cementite or graphite. This permits the alloy to be quenched more slowly than plain carbon steel. The copper and chromium hold the carbon in its combined. hardening form at. relatively high temperatures, which is of considerable advantage in tool and roll steels which are subjected to heat, because the steel will not soften in use at a temperature which would soften plaincarbon steel. This ability of the copper and chromium to hold the carbon in its combined state is particularly valuable in high carbon steels or high carbon cast iron, in that a high percentage of carbon may be kept in the hardening state. so as to-form a very'ihard article.

The silicon apparently tent acts in an additive manner toward augmenting the tensile strength derived from "the carbon and chromium contents, and also increases the ratio of elastic limit'to tensile strength. Also, the presence of copper does ,notinterfere in any way with the possibilities of heat treatment, thus allowing a latitude in the direction of a variation of physical properties.

The proportions of the chromium, copper, carbon and silicon may be varied over fairly wide ran es within the limits described, so thatcstee s ofdifi'erent physical properties may be produced, which will, however, have the desirable stain, rust and acid resisting properties.

In the foregoing description no reference has been made to the presence of other elements, such as manganese, sulphur, phosphorus, etc., which arealways present in steels and cast irons, as, their presence to the usual extent does not interfere with the physical or non-corrosive properties of the exact alloys.

v The present invention is not limited to the proportions above set forth as its preferred embodiment, but may be otherwise emb'odied withinthe scope of the following claims. I a a I claim:

1. A ferrous alloy containing carbon,

contents. On the contrary, the copper conabout 8 to 25% chromium, .5 to 5% copper to 6% silicon.

4. A ferrous alloy containing from 2% to 25% chromium, from 15% to,.5% copper.

and from .5% to 6% silicon, together with carbon.

5. A ferrous alloy containing over 2% chromium but not over the percentage of chromium in stainless steelsflfrom .15% to 5% copper and from .5% to 6% silicon, together with carbon.

6. A ferro alloy consisting principally of iron and containing over 2% chromium, .15 to 5% copper and .5% to 6% silicon, together with carbon.

7. A resistance surface alloy of iron comprising in combination with the iron, silicon from 1% to 6%, chromium to 10%, copper from ;5% to 5%.

s a new product, an .alloy steel comprising silicon from 1% to 6%, chromium from 2% to 10%, copper from .5% to 5%, carbon from .05% to 1%, and the balance iron.

9. As a new product, an alloy steel comprising silicon from 1% to 6%, chromium from 2% to 10%, copper from .5% to 5%, carbon from .1%- to 1%, and the balance lI'OIl.

In testimony whereof I have hereunto set my hand,

BYRAMJI D. SAKLATWALLA.

A resistant-surface alloy of iron comchromium from 3% I from 2% v 

